overbuilt benches

[dkff49]

I was asked in a thread over in hardware/software to show pictures of a doll bench that I make that will hold a full grown man of not so small proportions and only have 6 nails in with those only holding the back on. Being that I am so proud of this feat I thought instead of just sending it via PM I would share it with the WORLD or at least AH world.

Here some pics of the pattern.

Here is end of the bench. Note how the sliding dovetail joints form a 't' and that the short side of the 't' has a little bit of a taper, this is to allow the cross piece to side down into it.



Here is a pics of ends of the seat and cross piece. Though they don't show it well you can still somewhat tell there is a taper to the cuts and the tapered portion does not go quite to the end. This allows me to have the joint hidden in the front.



View with the ends, seat and cross piece assembled. There would normally be glue in those joints when the bench is put together for final assembly.



Close up



Assembled from front.



Assembled from back. This where the nails go. 2 nails centered on bottom of back going into the seat and 2 nails holding the back to the ends. Glue would also be put in these locations prior to assembly to increase the holding power and to ensure that the bench will never come apart and the very nice doll bench could even be used as a step stool when the wife is not looking.



All the sliding dovetails (male and female were made with a 3/8 dovetail router bit. This type of joinery takes a great deal of time and patience and some very straight boards. With that said it is also one of the strongest (if not the strongest) joints that can be made with wood.

[grizz441]

When it does break, how does it break?

[dkff49]

Well you could drive a car over it and watch it go to splinters other than that, Not really sure.

[caldera]

"Uh-huh-huh-huh-huh.  Wood."

"Yeah, yeah!  Booooiiiiinnnngggg!"


After you're done making Lawntard's desk, you can get started on mine. 

[dkff49]

hmmm

what kind of trade could i come up with here. 

thinking ride on a certain aircraft at WWII weekend.

[ebfd11]

"Uh-huh-huh-huh-huh.  Wood."

"Yeah, yeah!  Booooiiiiinnnngggg!"


After you're done making Lawntard's desk, you can get started on mine. 

LOL My desk is loooking good and I can't wait to be sitting at it and killing the Red Guys.

[bozon]

Cool! dkff49 is bulding a mosquito. Good luck with that project

[guncrasher]

if you gonna make a bench for lawntard, I am not a carpenter or anything, but may I suggest steel?  I dont think there's any kind of wood that will hold him  j/k.

If I can make a suggestion for his desk, dont forget the tequila holder.

semp

[Babalonian]

POTW wants to know if you have offer a custom trowel design as well?

[morfiend]

 DK,

  Try to do those dovetails by hand with a backsaw and chisels!   I had to do a bunch back in the day,it was part of getting a cabinet maker ticket.



  A word of caution,dont use alot of glue the dovetail is strong but meant to move as the wood shrinks and swells,if you use too much glue the male part can split and you'll loose all the strenght. You only need a couple of small drops of glue,one at each end and maybe a drop in the middle. A well made dovetail doesnt need glue in most cases. I'm not saying to not use glue..    just use it sparringly.




   

[dkff49]

I am sure I can come up with some kind of plan for a trowel.

Morfiend I don't think I have the patience to do those by hand. It pushes limits just trying to get it just right with the router. For the most part I haven't heard of any breaking or even appearing to be weak, so I guess I did ok. The biggest problem I found my self having was splitting out the sides of the female side by making it too tight. I completely see what your saying about too much glue though.

I haven't made one of these things in several years, it seems no one really wants to pay someone to take this much time to make anything any more. Quick and cheap seems to be the going trend these days, though I must admit these are a little overdone.

[grizz441]

Not to get all enjuneerin, but I'm surprised those "dove tail" endings don't just shear off under load.  I guess they are mostly under compression though.  That's why I was asking about when it breaks how does it break, because I was curious what governs the strength of it. 

[dkff49]

I get your point now Grizz, I thought you were being humorous with your response. 

I'm not really sure how it maintains it's strength and originally when I started making these I thought much the same, which is why I went with the largest dovetail bit I could find at the time.

There might be someone in here that could give a you an answer, from an engineering stand point, but in reality it was purely a guess and as to how strong this bench would be in the end.

[morfiend]

 Actually grizz has a good point,from what I can see you used the DT's as opposed to a buttjoint. From what I can make out from the pictures though,it looks like you have 2 dovetail jointed pieces at 90 degrees to each other so the verticle one would hold up the horizontal 1 and they will both hold the sides in place.

    Is this correct? it;s hard to tell from the limited views. If this is the case then ideally you'd want 2 horizontal pieces,1 in front and 1 in back to hold the seat up,like a front valance,that would take any load off the dovetail that makes up the seat of the bench.

    All of this is based on my assumption from what I can see!



   

[dkff49]

You would be correct Morfiend. The only thing is the only thing holding the horizontal piece in place is the glue as it slides up and down inside it's DT and with this glue joint would not be at it's strongest either due to being on end grain.

After some additional though, I believe the back has as much to do with the benches strength as the DT 's do. The back is also glued and nailed which helps as well. Any weight that is put on the seat of that bench would then be distributed to the end and horizontal DT's as well as across the whole back. Making the main purpose of the DT's to keep the ends in place without the use of any fasteners.

In all honesty I think the sides of the female would split out before the male side would shear off though. I say this only because that is where I have had problems before when assembling them. Most of the time my trouble came from the DT being too tight. If you look pretty close at the close up of the assembled end you can see there is where the material is lacking.